Wesseloo, J & Sweby, GJ 2008, 'Microseismic Monitoring of Hard Rock Mine Slopes', in Y Potvin, J Carter, A Dyskin & R Jeffrey (eds), SHIRMS 2008: Proceedings of the First Southern Hemisphere International Rock Mechanics Symposium, Australian Centre for Geomechanics, Perth, pp. 433-450, https://doi.org/10.36487/ACG_repo/808_179 (https://papers.acg.uwa.edu.au/p/808_179_Wesseloo/) Abstract: Open pit mine slopes are likely to increase in depth in the future. With this comes an increased stress environment and a greater uncertainty regarding the mechanical behaviour of the slopes. Microseismicity detectable in the slope provides a valuable source of information about its mechanical behaviour. Microseismic monitoring has been used at several large natural rock slope, civil and open pit mine slopes with varying degrees of success. In spite of some operational difficulties experienced at different sites, the method shows a lot of promise. The paper gives an overview of microseismic monitoring of rock slopes and discusses the measured seismicity at an open pit mine in Australia relative to the in situ stress state. Fracture initiation at the site occurred at stress levels below the expected rock mass strength and appears to be consistent with both the conceptual model for the development of instability in hard rock slopes suggested by Eberhardt et al. (2004) and Stead et al. (2007), as well as the concepts underlying the cohesion-softening-friction-hardening constitutive models.